The present invention relates to an endless cassette tape for a video tape recorder (to be referred to as a VTR hereinafter).
Two types of cassette tapes are currently used for VTRs throughout the world: cassette tapes of the Betamax system and of the VHS system.
In a VHS cassette tape, as shown in FIG. 1, a video tape 4 is wound around a supply reel 2 and a take-up reel 3 arranged inside a cassette 1. When cassette 1 is loaded (to be referred to as automatically loaded hereinafter), the front cover of the cassette automatically opens as shown in FIG. 2. Through this opening, video tape 4 is drawn outside the cassette by means of a movement guide post 5 guiding the video tape, conical guides 6 and 7, a movement guide post 8, and a capstan 9. The part of video tape 4 drawn out of cassette 1 (to be referred to as a slack part) is threaded past a full-width erase head 10, a roller 11, a video head 12, a roller 13, an audio head 14, and a pinch roller 15. Then, video tape 4 is driven at normal speed by the pinching action between the capstan and the pinch roller. In FIG. 2, reference numerals 16 and 17 denote tension posts; 18 and 19, guide poles; 20, a spring plate; and 21, a pad plate.
When the eject button is depressed, video tape 4 is taken up completely by supply reel 2 in the direction indicated by a dotted arrow while movement guide post 5, conical guides 6 and 7, movement guide post 8, and capstan 9 return to the positions shown in FIG. 1. When the slack part is completely wound onto supply reel 2, the front cover of the cassette automatically closes. Then, cassette 1 is disengaged from a reel spindle and can be ejected.
In a Betamax cassette, as shown in FIG. 3, a video tape 24 is wound around a supply reel 22 and a take-up reel 23 arranged inside a cassette 35. When tape 24 is automatically loaded, the front cover of cassette 35 automatically opens as shown in FIG. 4. Then, video tape 24 is drawn out of cassette 35 by movement guide posts 25 and 26 guiding the tape, a capstan 27, and a guide post 28. Thus, the slack part of video tape 24 is formed. Tape 24 is brought into contact with a full-width erase head 29, a video head 30 and an audio head 31 to start travelling at normal speed. When the eject button is depressed, video tape 24 is taken up by take-up reel 23 while movement guide posts 25 and 26, capstan 27 and guide post 28 return to their original positions shown in FIG. 3. When the slack part of video tape 24 is completely taken up, the front cover automatically closes. Thereafter, cassette 35 can be disengaged from a reel spindle and can be ejected outside the VTR. Referring to FIG. 4, a loading ring 32 serves as a mount for guide post 26, capstan 27, and guide post 28. Tape guide posts 33 and 34 are also mounted on loading ring 32.
As may be seen from a comparison of the figures, the length of the slack part of the video tape which is drawn outside the cassette and which is originally kept taut between the two reels in the cassette significantly differs from the Betamax type to the VHS type.
In a cassette of the Betamax system, the slack part assumes an omega shape in plan view and the length thereof exceeds about 40 cm. However, in a cassette of the VHS type, the slack part is M-shaped in plan view with a length of about 25 cm. The basic structures and the tape suspending mechanisms are significantly different in cassettes of the Betamax system and the VHS system.
To house an endless tape of 1/2 inch width in a cassette of the type wherein the slack part must be automatically eliminated before ejection of the cassette, a totally new mechanism must be adopted which is different from that widely used for cassettes of endless tapes of 1/4 inch width or less.
In an endless tape cassette of 1/4 inch width or less of known type, the portion of the tape at the inner periphery of the tape coil is drawn out to pass it past the recording and reproducing parts, and is then wound around the outer periphery of the tape coil. This inevitably results in a structure wherein the drawing part of the tape and each turn of the tape coil cross each other in a stepped form. Due to this structure, it has been impossible to draw the video tape outside the cassette and to automatically take up the slack part thus formed by pivotal movement of the take-up reel.